Method and device for detecting the position for a crease line of a packaging web

Abstract

The position of a transverse crease line of a moving packing web is sensed in that light reflected from the web and emanating from a laser directed perpendicularly to the web is received by photo detectors from two directions in the direction of movement of the web and under an angle of for example 60° in relation to the light beam directed to the web. The electrical measuring signal emanating from the photo detectors is compared in an electronic signal processor with a reference signal, which is stored in the processor and is representative of a reference crease line. A crease line is indicated when the value of a correlation signal, which constitutes a calculation of conformity between the measuring signal and the reference signal, reaches a maximum. In a corresponding way, the position of a longitudinal crease line can be sensed.

I claim: 
     
       1. A method for determining the position of a crease line or similar embossment in a moving packing web, the steps comprising; (a) directing at least one light beam perpendicularly against the surface of said moving packing web,   (b) detecting two reflected lights from said at least one light beam as reflected from said moving packing strip at oblique angles to, and on either side of, said at least one light beam,   (c) creating an electrical signal characteristic of each said two reflected lights,   (d) converting and combining each of said electrical signals to form a measuring signal,   (e) comparing said measuring signal to a reference signal representative of a reference crease line, and   (f) determining the position of said crease line or similar embossment in said moving packing web, as being where the correlation between said measuring signal and said reference signal is at a maximum.   
     
     
       2. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said light beam is an oscillating light beam. 
     
     
       3. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said light beam is a laser light beam in the shape of a slot transverse to a direction of movement of said moving packing web. 
     
     
       4. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said reflected lights are detected by photo detectors. 
     
     
       5. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said reflected lights are reflected at angles to said at least one light beam of more than 30°. 
     
     
       6. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said measuring signal is sampled with a predetermined feeding length of said packing web as a basis. 
     
     
       7. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said two reflected lights are symmetrical with respect to said at least one light beam. 
     
     
       8. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 7, in which said one light beam is an oscillating light beam. 
     
     
       9. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 7, in which said one light beam is a laser light beam in the shape of a slot transverse to a direction of movement of said moving packing web. 
     
     
       10. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 7, in which each of said two reflected lights are detected by an individual photo detector. 
     
     
       11. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which each of said two reflected lights are reflected at an angle to said light beam of more than 30° on each side thereof. 
     
     
       12. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which said measuring signal is a quotient between the difference between the two electrical signals and the sum thereof. 
     
     
       13. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 1, in which two said light beams are directed obliquely against a point on said surface of said moving packing web, from opposite directions at equal angles to a line perpendicular to said point on said surface of said moving packing strip, such that each said light beam will cause a said reflected light, each of said reflected lights being reflected substantially perpendicularly away from said surface of said moving packing strip and generally aligned with each other. 
     
     
       14. A method for determining the position of a crease line or similar embossment in a moving packing web, according to claim 13, in which both of said reflected lights are detected by a photo detector array disposed in a substantially perpendicular relationship to said moving packing strip. 
     
     
       15. A method for determining the position of a crease line or similar embossment in a moving packing web, the steps comprising; (a) directing light beam perpendicularly against the surface of said moving packing web,   (b) detecting a first reflected light from said light beam as reflected from said moving packing strip at a first oblique angle to said light beam, and creating a first electrical signal characteristic of said first reflected light,   (c) detecting a second reflected light from said light beam as reflected from said moving packing strip at a second oblique angle to said light beam, and creating a second electrical signal characteristic of said second reflected light,   (d) combining said first and second electrical signal to create a measuring signal,   (e) comparing said measuring signal to a reference signal representative of a reference crease line, and   (f) determining the position of said crease line or similar embossment in said moving packing web, as being where the correlation between said measuring signal and said reference signal is at a maximum.   
     
     
       16. Apparatus for determining the position of a crease line or similar embossment in a moving packing web, said apparatus comprising; (a) a light source for directing at least one light beam against the surface of said moving packing web,   (b) at least one means for detecting reflected light from said at least one light beam reflected from said moving packing strip at an oblique angle to said at least one light beam, and for creating an electrical signal characteristic of said reflected light,   (c) a signal processor for creating a measuring signal representative of said reflected light, and comparing said measuring signal to a reference signal representative of a reference crease line, and   (d) said crease line or similar embossment in said moving packing web, being where the correlation between said measuring signal and said reference signal is at a maximum.   
     
     
       17. Apparatus for determining the position of a crease line or similar embossment in a moving packing web, according to claim 16, in which said light source directs a single light beam against the surface of said moving packing web at an angle substantially perpendicular to said moving packing web, and said at least one means for detecting reflected light comprises two means for detecting reflected light from said one light beam, a first for detecting a first reflected light and creating a first electrical signal representative of said first reflected light, and a second for detecting a second reflected light and creating a second electrical signal representative of said second reflected light, and said signal processor create said measuring signal by combining said first and second electrical signals. 
     
     
       18. Apparatus for determining the position of a crease line or similar embossment in a moving packing web, according to claim 17, in which said single light beam is a laser light beam in the shape of a slot transverse to the direction of movement of said moving packing web. 
     
     
       19. Apparatus for determining the position of a crease line or similar embossment in a moving packing web, according to claim 16, in which at least two light sources are provided to direct a pair of light beams against the surface of said moving packing web at equal oblique angles to a point on said surface of said moving packing web, from opposite directions at equal angles to a line perpendicular to said point, and said at least one means for detecting reflected light comprises a single means for detecting reflected light reflected perpendicularly from said point on said surface of said moving packing web. 
     
     
       20. Apparatus for determining the position of a crease line or similar embossment in a moving packing web, according to claim 19, in which said single means for detecting reflected light reflected perpendicularly from said point on said surface of said moving packing web is adapted to detect two reflected lights aligned with each other.